Attending personal therapy sessions is a requirement in many counselling and psychotherapy trainings worldwide. More research is needed to establish why the requirement is essential and what it is intended to achieve. This study focused on the question, "what is the rationale for mandated self-development requirements in therapy trainings?" From a selective literature search, 19 highly relevant papers were found which formed a sampling frame. The papers included qualitative studies, mixed method reports, review and opinion papers. Research participants across all reports included therapy and psychiatry trainees (N = 1134), and current therapy practitioners (N = 194) totalling 1328 participants. The papers were analysed using Critical Interpretive Synthesis method to devise a synthesising statement. The analysis resulted in a synthesising statement about the rationale for personal psychotherapy during training, and the stated risks of this requirement as reflected in the materials consulted. A strong coherent rationale exists for the recommendation that trainee therapists undertake personal psychotherapy. However, the risks of mandating this requirement present multiple challenges, and the evidence for the intended outcomes of personal psychotherapy undertaken during training is weak.